US President Donald Trump has threatened that "a whole civilisation will die tonight, never to be brought back again" if Iran does not comply with his demands, marking his most extreme warning yet in the rapidly escalating conflict.
The latest ultimatum builds on earlier threats to carry out "complete demolition" of Iran's infrastructure, including destroying all power plants and targeting bridges, oil facilities and desalination plants.
He had set a Tuesday evening as a deadline for Iran to reopen the Strait of Hormuz.
Trump has also explicitly threatened to destroy "every bridge and every power plant in Iran", signalling a notable shift away from targeted military strikes toward far broader and more indiscriminate destruction.
US-Israeli strikes on infrastructure have already been reported, including bridges, railway lines and highways.
Rights groups have strongly condemned the rhetoric. Amnesty International Secretary General Agnes Callamard said Trump’s threats show a "staggering level of cruelty and disregard for human life", warning that targeting civilian infrastructure could have "catastrophic consequences for over 90 million people".
She added that such statements may amount to a threat to commit genocide under international law, which defines the crime as acts carried out with the intent to destroy, in whole or in part, a national, ethnic, racial or religious group. Why could these threats amount to war crimes? Deliberately targeting infrastructure essential to civilian survival may violate international humanitarian law.
Under the Geneva Conventions, objects indispensable to civilians, such as electricity and water systems, are protected, and while infrastructure can be targeted if it has a military use, attacks must be proportionate and minimise harm to civilians.
Amnesty warned that intentionally attacking civilian infrastructure, including power plants, water systems and energy networks, would likely be disproportionate and could constitute war crimes, as these systems are essential for access to healthcare, food and basic livelihoods.
Former US military lawyers Margaret Donovan and Rachel VanLandingham wrote on Just Security that carrying out such large-scale attacks could amount to "the most serious war crimes".
UN Secretary-General spokesperson Stephane Dujarric has warned that such attacks are prohibited if they risk "excessive incidental civilian harm".
Spanish Foreign Minister Jose Manuel Albares has also warned that any attack on civilian infrastructure in Iran would constitute a war crime under international law, cautioning that such actions would have "incalculable" economic and social consequences and could lead to catastrophic impacts on civilians
The scale of destruction being threatened is key, as while individual strikes on infrastructure can sometimes be lawful, destroying systems "en masse" to pressure a government would likely fall outside legitimate military objectives and raise serious legal concerns. What legal rules are being tested? At the centre of the issue are the principles of distinction, proportionality and military necessity. A target is only lawful if it makes an effective contribution to military action and offers a definite military advantage, a threshold that must be assessed on a case-by-case basis rather than through blanket targeting.
Even when infrastructure has dual use, attacks must avoid disproportionate harm, and destroying entire national systems, such as power grids, is widely seen as unlikely to meet that threshold.
Attacks aimed at "politically coercing" an opponent or inflicting widespread suffering, rather than achieving a concrete military objective, would not be lawful and risk breaching the core rules governing armed conflict. Does intent and scale matter? Yes, and this is where much of the concern lies, as Trump's rhetoric suggests a shift toward collective punishment, targeting infrastructure that sustains the civilian population as a means of pressure.
That would represent a significant escalation beyond strikes aimed at military capabilities and blur the line between military objectives and civilian harm.
Experts say that even if some infrastructure could be considered dual-use, the indiscriminate nature and scale of the proposed attacks could render them unlawful.
As one legal expert cited by Vox put it, such "indiscriminate attacks" could amount not just to violations of the laws of war, but to war crimes for those involved. Why does this put US military officers in a bind? Trump's threats create a dilemma for US service members, who may be forced to choose between following orders and risking involvement in potential war crimes.
Under US military law, personnel must refuse "manifestly unlawful" orders, yet doing so carries risks, including prosecution for insubordination.
Historical precedent shows that following orders is not a defence if those orders are clearly illegal, with the My Lai massacre case during the Vietnam War establishing that unlawful orders must not be obeyed.
While many soldiers understand this duty in theory, cases from Iraq show that refusal is rare in practice, even when the legality of a war or specific actions is widely questioned. Could Trump be held accountable? Accountability for a sitting US president is unlikely to come through international courts and would depend largely on domestic political processes.
Neither the United States nor Iran recognises the International Criminal Court, limiting avenues for prosecution, although war crimes can theoretically fall under universal jurisdiction.
In practice, any action would likely depend on Congress, which would need significant political backing, while legal protections for the president, including immunity and pardon powers, further complicate any path to accountability. What are the wider consequences? Beyond legality, experts warn of severe humanitarian and strategic fallout as the conflict intensifies.
Strikes on infrastructure have already caused civilian casualties and disrupted transport routes, while Iran has warned it could retaliate by targeting global energy supplies, raising fears of a wider regional escalation, particularly after previous attacks on Gulf states including strikes on energy facilities in Saudi Arabia, the Ras Laffan LNG site in Qatar, and airports and industrial sites in the UAE that caused major disruption.
Trump's rhetoric has also heightened fear among civilians inside Iran, with one resident telling AFP that "death is not a joke". Amnesty said the threats are already "terrorising millions of people in Iran and their distressed relatives abroad", warning that further escalation could plunge the country into a prolonged humanitarian crisis.